1. Field of the Invention
This invention relates to a zoom lens capable of macro-photography.
2. Description of the Prior Art
A zoom lens is already known which includes a focusing lens group, a variator group, a compensator group and a master lens group and in which one of the variator group and the compensator group is moved for macro-photography (focusing) by an operation different from the normal zooming operation.
There is also known a so-called one-hand zoom lens of the type in which zooming and focusing is effected in response to the movements of an operating ring in two directions, namely, a longitudinal or axial movement with respect to the optical axis of the lens and a rotational movement about the optical axis of the lens.
To provide such a one-hand zoom lens with a macro-photography function, Japanese Utility Model Laid-Open Publication No. 2436/1979 discloses a close-up distance adjusting device in an interchangeable zoom-type lens for a camera wherein a first lens group is supported by an outer barrel slideable axially back and forth while rotating relatively to a main body and normally effecting distance adjustment. A plurality of zoom lens groups is provided for effecting zooming by changing the relative position thereof. The groups engage a plurality of cam grooves in a zoom cam barrel rotatable relative to a main body. Each of said cam grooves is further extended from the position of the shortest focal length to form a cam groove extension, in which are disposed an outer barrel connecting member connected to an outer barrel to receive only the rotation thereof relatively to the main body and a zoom barrel connecting member connected to the zoom cam barrel and rotatable relative to the main body and slideable back and forth relative to the zoom cam barrel. A cam is provided on one of said two connecting members and a cam follower is provided on the other connecting member for cam engagement, so that the zoom cam barrel can be induced into rotation along a cam extension only when the first lens group has been located at the closest distance position and the zoom lens groups have been located at the position of the shortest focal length. However, in this device, the change-over to macro-photography becomes possible only after the lens groups have been preset to predetermined positions. This has the disadvantage that macro-photography cannot be accomplished at any desired focal length within the zooming range.